1. Field of the Invention
The present invention relates, generally, to a communication system for switching data packets between connected communication terminals and, more specifically, to a communication system for switching data packets with allocated items of routing information between communication terminal apparatuses of the communication system and/or communication terminal apparatuses in a local network wherein the communication system includes at least one network coupling unit in the form of a subscriber terminal unit such that time-division-multiplex-oriented terminals which are also arranged in the communication system may be directly connected via the coupling unit.
2. Description of the Prior Art
In known communication systems, connections to a public or private communication network near the communication system are created through primary multiplex terminal units (also called S2 terminals) arranged in the system itself; a communication network taking the form for example, of an ISDN-oriented communication network. Via an S2 connection, a local network --(-- e.g., an Ethernet LAN that connects several personal computers --)-- can be connected with the ISDN-oriented communication network via a router. For this purpose, the router is equipped with both an S2 interface and a LAN interface in accordance with standards, wherein the S2 interface is connected with the output of the S2 terminal unit of the communication system and the LAN interface of the router is connected with the local network.
With respect to its essential function, a router is formed as layer 3 of the OSI reference model, wherein with the aid of router networks is connected physically with the respectively different topology of layers 1 and 2 --(-- e.g., Ethernet LAN and ISDN-oriented communication network. In order to switch data packets between the networks connected to the router, the address indications contained in the routing information of the data packets --(-- destination and source --)-- are interpreted by a control device arranged in the router wherein are evaluated, and the data packets are subsequently converted correspondingly.
The S2 interface has 30 useful channels that can be used only with larger local networks. This means that the S2 interface is not optimally utilized; i.e., the useful channels are physically assigned and cannot be used for other communication terminal apparatuses.
In U.S. Pat. No. 5,208,811, for example, a communication arrangement is described in which a plurality of LAN communication terminal apparatuses, arranged in a local communication network LAN, are connected via a separate network coupling unit (LAN/ISDN interworking unit) to an ISDN-oriented communication network with ISDN communication terminal apparatuses arranged therein. Given a connection setup, initiated by a LAN communication terminal apparatus, to an ISDN communication terminal apparatus, the network coupling unit transmits an ISDN channel number and an item of DLCI (Data Link Connection Identifier) information, representing an ISDN communication path, to the LAN communication terminal apparatus. This apparatus subsequently transmits a LAN data frame, containing an item of communication path information, to the network coupling unit. After reception of the LAN data frame, the network coupling unit carries out a format conversion in which the LAN data frame is converted into an ISDN data frame.
In addition, in U.S. Pat. No. 5,351,237 a communication arrangement is specified in which a multiplicity of local networks, LANs, are connected to an ISDN-oriented communication network via a multiplicity of network coupling units or, respectively, routers. Of the routers arranged in the communication arrangement, one is configured as a higher-order router (main router) and the remaining routers are configured as lower-order routers (sub-routers). Each router has a table in which items of router information are stored. Given an updating request initiated by a sub-router, items of router information updated by the main router are transmitted to the sub-routers in the form of data packets, wherein, using the received items of router information, each sub-router updates the items of router information stored in the tables.
The present invention, therefore, is based on the object of improving the coupling of communication systems, private branch exchanges, and local networks.
The essential aspect of the inventive communication system for switching data packets with allocated items of routing information between communication terminal apparatuses of the communication system and/or communication terminal apparatuses in a local network is that at least one network coupling unit in the form of a subscriber terminal unit, is arranged in the communication system. The communication system thereby includes a coupling field module that has a plurality of bidirectional terminals that operate according to a time-division-multiplex transmission method, and further includes a control unit that is connected with the coupling field module and has at least one signaling terminal. According to the present invention, the network coupling unit has at least one LAN terminal unit having a LAN interface for connection to a first local network, as well as at least one multiplex unit, which realizes a bidirectional output that operates according to a time-division multiplex transmission method, for connection to at least one of the bidirectional time-division-multiplex-oriented terminals of the coupling field module. In addition, in the network coupling unit there is arranged a signaling unit that includes a signaling output, for connection to the at least one signaling terminal of the control unit, and a conversion unit that is connected with each of the multiplex unit, the signaling unit and the LAN terminal unit. The conversion unit has means for the evaluation of the routing information, and means for switching the data packets from and to the local network or, respectively, from and to the coupling field module, depending on the result of the evaluation. The conversion unit also has means for the conversion, in accordance with a first transmission protocol, of items of signaling information into items of signaling information in accordance with at least one additional transmission protocol, and means for the adaptation of the data format of the data packets that are to be switched in accordance with either the first or the at least one additional transmission protocol.
The essential advantage of the inventive communication system is that through the construction of the network coupling unit as a subscriber terminal unit that can be integrated into the communication system, the time-division-multiplex-oriented terminals, arranged in the communication system, of the coupling field module are connected directly, via the network coupling unit or, respectively, via the conversion unit arranged therein, with the local network connected to the communication system. In this way, data packets that are transmitted to the communication system or, respectively, to the network coupling unit and that include an item of routing information can be switched between the networks connected to the communication system. Through the arrangement of router functions in the network coupling unit, it is possible to do without a financially costly connection of an external router (for example, an ISDN router or access server) including the S2 interface realized in the communication system. It is, thus, also possible to create an economical switching-oriented connection between a local network (for example, Ethernet LAN) and the communication network (for example, a private corporate network or a public ISDN-oriented network). The local network can, for example, be constructed as a communication system-internal administration network having a plurality of administration servers and maintenance servers connected thereto. An external administration central station, arranged in the public communication network, can thus dial into the communication system via the public communication network and can gain access (xe2x80x98dial-in functionxe2x80x99) to the desired communication system-internal local network or, respectively, to the administration and maintenance servers connected thereto via the inventive network coupling unit. Through the inventive network coupling unit, and the possibility created thereby of remote administration of a communication system, the administration and maintenance of a communication system, in particular of larger switching installations, is simplified considerably.
The network coupling unit advantageously has at least one additional LAN terminal unit connected to the conversion unit, having an additional LAN interface for connection to at least one additional local network. For this purpose, in the conversion unit there are arranged additional means for the switching of the data packets from and to, and between the local networks or, respectively, from and to the coupling field module. In the conversion unit there are also arranged additional means for conversion from and into items of signaling information according to an additional transmission protocol, or items of routing information, and additional means for the adaptation of the data format of the data packets. Through the LAN terminal unit additionally arranged in the network coupling unit, an additional local network (also designated server/customer LAN) can be connected to the network coupling unit and, thus, to the communication system. Through the means arranged in the network coupling unit (router functions), an exchange of data between the two connected local networks is additionally enabled.
Given additional communication systems connected with one another and forming a communication network, the conversion unit has additional means for switching the data packets between communication terminal apparatuses of the communication system and one of the connected local networks, or between the additional communication systems of the communication network and a local network. The conversion unit also has means for the corresponding conversion of the signaling functions, and means for the corresponding adaptation of the data format of the data packets. In this way, a service server which is arranged, for example, in the communication network, can create a connection to a server that is connected with the server/customer LAN of a communication system. This server that is connected with the server/customer LAN can, for example, be constructed as a phone mail server.
According to an embodiment of the inventive communication system, the network coupling unit has means for the unambiguous LAN identification of a LAN interface inside a local network, means for the unambiguous logical network identification of the LAN interfaces and of communication terminal apparatuses of the local networks --(-- the LAN interfaces and the communication terminal apparatuses being allocated to a higher-order network --)-- and means for the communication network identification of the network coupling unit inside the communication network. The unambiguous LAN identification of a LAN interface thereby corresponds to an addressing that has settled in layer I of the OSI reference model, and the logical network identification corresponds to an addressing that has settled in a higher layer (layer 3). Both the unambiguous LAN identification and the logical network identification of a LAN interface are unambiguously valid worldwide; i.e., the LAN interface identified thereby can be addressed under an identification or, respectively, address that is unambiguously valid worldwide. Such is advantageous under the widely distributed Internet protocol or, respectively, Internet address. Through the named means for the identification of the LAN interface or, respectively, of the network coupling unit, the named units or, respectively, interfaces can be addressed using different standardized network access mechanisms or, respectively, network protocols. The network protocols thereby can be arranged on different levels of the OSI reference model, wherein standardized and widely available application software can be used for the exchange of data between the connected networks.
Optionally, the network coupling unit has additional means for the additional local logical network identification of a LAN interface, including the allocated local network. Through this means, a LAN interface already having a global logical network identification can be assigned an additional local logical network identification which, however, is valid only inside the local network connected to the LAN interface. The assignment of local logical network identifiers inside a local network has the advantage that no network identifications or, respectively, Internet protocol addresses that are valid worldwide need be assigned for, e.g., communication terminal apparatuses that are internal to the communication system.
According to an embodiment of the present invention, the unambiguous LAN identification of a LAN interface is in the form of an interface-related standardized LAN address, the logical network identification of a LAN interface is in the form of a standardized Internet address, and the communication network identification of the network coupling unit is in the form of a communication network call number. The interface-related standardized LAN address is for example formed by a hardware address or, respectively, MAC (Medium Access Control) address of a LAN or Ethernet interface. It is six bytes long and is assigned unambiguously worldwide by IEEE. A MAC address is allocated to each LAN interface arranged in the network coupling unit. They are advantageously stored in a PROM during the manufacturing of the assembly and cannot be configured. The standardized Internet protocol address, global or local, is an address of layer 3 of the OSI reference model. In general, this identifies both the LAN interface and the local network connected with the interface. For the case of a provision of a global Internet access through the communication system, the Internet address must be unambiguous worldwide. The Internet address must be unambiguous at least in the networks to which the LAN interfaces arranged in the network coupling unit or, respectively, the bidirectional, time-division-multiplex-oriented outputs have access via the communication network. The Internet addresses can be configured freely.
For the switching of the data packets, means are provided in the network coupling unit for the recognition of the data packet heads. Also, means are provided for the selection of the network identifications arranged in the data packet heads as well as means for the evaluation of the network identifications. In addition, the network coupling unit has means for switching the data packets depending on the result of the evaluation; either to a local network connected to the network coupling unit or to the communication network. Through this advantageous embodiment of routing functions in the network coupling unit, the destination addresses contained in the heads of the data packets are selected, evaluated and subsequently switched to the corresponding destination.
Upon the recognition of data packets to be switched via the communication network, additional means are provided in the network coupling unit for the conversion of the logical network identification into a communication network identification, wherein the communication network identification is formed depending on the logical network identification. In addition, means are provided for the connection setup via the communication network with the communication network identification, and means are provided for the forwarding of the data packets via the set-up connection. This advantageous design enables the setting up of connections to other communication systems arranged in the communication network or, respectively, to the network coupling units arranged therein, the connection is set up via the communication network depending on the logical network identifications contained in the data packets. For this purpose, a corresponding network identification is derived from the logical network identification or, respectively, the logical network identification is converted into the corresponding communication network identification.
For the conversion, memory means are preferably arranged in the network coupling unit for the storing of additional logical network identifications of additional local networks, or, respectively, additional LAN interfaces, arranged in the communication network. In addition, memory means are provided for the allocation of communication network identifications representing an additional network coupling unit, to the stored additional logical network identifications of the additional networks. Through this advantageous design, the logical network identifications selected from the data packet heads are compared with the stored external logical network identifications of the additional external --(-- or, respectively, arranged in the communication network --)-- local networks or, respectively, LAN interfaces and, upon recognition of a stored logical network identification having an allocated communication network identification, the corresponding connection is set up via the communication network on the basis of the communication network identification wherein the data packets are switched to the destination.
Upon the recognition of data packets to be switched to a local network connected to the network coupling unit, means are provided for the recognition of specific network identifications as well as for the conversion of the recognized network identifications into additional local logical network identifications. Also, means are provided for the insertion of the additional local logical network identifications into the data packets as well as for the adaptation and forwarding of the data packets. Through this advantageous design, given data packets that are to be switched to a local network (internal to the communication system) with an allocated local network identification, the logical network identifications are converted into the corresponding local logical network identifications, and the correspondingly adapted data packets are switched within the network internal to the communication system.